Luminaire

ABSTRACT

Corridor illumination with globular source embraced by a moldable lens whose interior and exterior surfaces are prismatic and coordinated with the reflectances of the floor, walls and ceiling of the corridor ultimately to distribute the lenstransmitted-light in the proportions of about 35 percent to the floor, 25 percent to each sidewall, and 15 percent to the ceiling.

United States atent Inventor Arthur W. Matteson Webster Groves, Mo. Appl. No. 793,813 Filed Jan. 24, 1969 Patented Aug. 17, 1971 Assignee The Edwin F. Guth Company Saint Louis, Mo.

LUMHNAIRE 9 Claims, 27 Drawing Figs.

US. Cl 240/78 LD, 240/78, 240/78 H, 240/106 R Int. Cl F215 1/06 Field of Search.....' 240/78, 78 H, 78 LD,106,106.1

References Cited UNITED STATES PATENTS 11/1957 Francketal 2,887,568 5/1959 Franck 240/106X 2,913,575 11/1959 Lipscomb 240/5111 FOREIGN PATENTS 240,470 5/1965 Austria 240/106 OTHER REFERENCES The Starglow by Modern, Modern Lighting Co., of St. Louis, illuminating Engineering, Sept., 1960 page 43a Primary Examine r-Samuel S. Matthews Assistant Examiner-Richard M. Sheer Attorney-Paul M. Wenk ABSTRACT: Corridor illumination with globular source embraced by a moldable lens whose interior and exterior surfaces are prismatic and coordinated with the reflectances of the floor, walls and ceiling of the corridor ultimately to distribute the lens-transmitted-light in the proportions of about 35 percent to the floor, 25 percent to each sidewall, and 15 percent to the ceiling.

PATENTED AUG 17 |97l SHEET 01 HF 12 FIG! PATENTED AUG I 7 |97l SHEET 05 0F 12 fl ill $1 PATENTEU AUG I H971 sum as or 12 Fl G1 0 Frizz/V6);

PATENTEI] AUG! 7191:

SHEET 07 0F 12 TESO/V PATENTED AUG] 7197! saw us or 12 PATENTEU AUG I 7 mm SHEET 10 0F 12 FIG 2| PATENTED AUG] 7 |97| SHEET 12 0F 12 LUMINAIRE The invention relates to illumination, and particularly to the illumination of corridors.

A corridor is a long, narrow room, typically 8 or 10 feet wide, with an 8-foot ceiling, to provide access to, and egress from, adjacent larger room areas, or from the out-of-doors. As the transition area between high luminances, light levels for corridors should be at least one-fifth of that found in adjacent room areas for proper eye adaptation,comfort and safety. This dictates that the illumination level for the floor of a corridor be in the range of 20 to 50 foot candles. Difficulty has heretofore been experienced in providing overall brightness balance between floor, walls and ceiling in corridors. Seen lengthwise, as corridors must be, the field of view simultaneously encompasses floor, walls, ceiling, and the lighting fixture itself. While excessive brightness contrast in any part of the corridor substantially reduces the eye adaptation level, thereby defeating the primary objective, as well as the aesthetic value of both the corridor and the illumination fixture; such brightness contrast is especially objectionable when it involves glare addressed in the normal line of sight of a person walking through the corridor.

In addition to being traffic areas, corridors frequently house lockers or exhibit cases along the walls, and the walls often carry bulletin boards, directive signs, paintings, school work exhibits, etc. Adequate corridor lighting features should provide proper and sufficient wall light distribution to assure convenience and good housekeeping, as well as adequate illumination on wall-mounted material, without auxiliary lighting equipment.

I-Ieretofore, the accepted principle of corridor lighting was to concentrate the light on the floor at a sacrifice of directwall illumination, but this creates tunnel effects.

It is therefore the primary object of the invention to improve corridor illumination.

A further object of the invention is to provide a luminaire having a moldable lens which directs the emitted light in a manner such as to achieve brightness balance, and eliminate tunnel effects in corridors, without glare addressed in the normal line of sight of a person traversing the corridor.

Visual brightness from corridor surfaces arises from light being reflected to the eye from each such surface. The amount of light reflected from a surface is the product of the amount of light incident upon that surface times the reflection factor of that surface. The invention contemplates the achievement of brightness balance in corridors by coordinating the light distribution pattern of the lens with the reflection factors of the several surfaces (floor, walls and ceiling) which bound the corridor so that, of the ultimate total, direct and interreflected light, approximately percent is addressed ceilingward, approximately 25 percent is addressed toward each of two sidewalls, and approximately 35 percent toward the floor. More specifically, with an incandescent lamp, when the corridor floor has a reflection factor of about 30 percent and the sidewalls of 50 percent, the source light should be so distributed by the lens that 60 to 65 percent thereof is addressed floorward in a zone of maximum intensity which flares crosswise of the corridor at least 25 each side of nadir; and substantially the balance of the source light is addressed in substantially equal proportions toward the respective sidewalls of the corridor.

These results are accomplished, in accordance with the present invention, by providing a corridor illuminating fixture having a globular light source, such as an incandescent or mercury vapor lamp, disposed within an appropriate reflector and confined by a light-transmitting lens having prismatic surfaces on both the interior and exterior faces thereof which refract and/0r reflect the source light in the course of transmitting it.

The invention contemplates lenses which are dish-shaped preferably square, or substantially so, in perimeter, and consist essentially of opposite end walls intervened and interconnected by convergingly related bottom sections. Both the end walls and the bottom sections have prismatic surfaces on both the interior and the exterior faces thereof, and the interior prisms are so oriented relative to the exterior prisms that, at

any given increment of lens, the apices of the prisms on the interior are right-angularly related to those on the exterior, that is to say, that the prisms on the inside of the lens at such increment may have their apices running horizontally, whereas the prisms on the exterior of that increment have their apices running vertically, or vice versa, thereby forming a grid.

The lens of the invention is further characterized by the feature that its opposite end walls are substantially vertical, and addressed lengthwise of the corridor. The end walls are interconnected by a trough-shaped portion which serves both as a bottom and as sides, through which the transmitted light is directionally controlled to distribute it to the floor and the sidewalls of the corridor as aforesaid. Being trough-shaped, there are opposite sections whose interior and exterior prism apices are oppositely oriented as above described, which sections converge downwardly toward nadir, preferably at an angle of between 50 and 75 between nadir and the respective sections. Each such section has, on the interior thereof, an array of prisms whose apices are substantially parallel with each other and with normal to nadir, the prisms in this array preferably having dihedrals greater than and addressed generally toward the globular light source. On the exterior of these sections, there is a right-angularly oriented array of prisms having parallel apices and whose dihedrals are acute and defined by one face which is substantially vertical and another face which slopes upwardly and endwardly from the downward extremity of the vertical face; and the acuity of such dihedrals progressively increasing from the longitudinal (i.e., in the lengthwise direction of the corridor) midpoint toward the ends of the lens. Such progressive increase in acuity compensates for the increasingly off-nadir aspect of light rays from a given point on the source as their point of incidence moves toward either end of the lens.

On the other hand, the obtusity of the dihedrals on the interior face of the trough sections progressively diminishes (crosswise of the corridor) toward the outer edges thereof, but in the case of wide corridors, it may be desirable to provide, immediately adjacent the outer edges, an array of three or four prisms whose dihedrals are even less obtuse than those closest to the middle, thereby to increase the light intensity at the comers between the floor and the sidewalls of the corridor.

Two embodiments of the invention are illustrated in the accompanying drawings, in which:

FIG. 1 is a perspective view of a relatively wide corridor in the ceiling of which two fixtures of the present invention are shown mounted;

FIG. 2 is a perspective view of the lens shown in the fixture of FIG. 1;

FIG. 3 is a top plan view of the lens shown in FIG. 2, showing the source-addressed face of its bottom;

FIG. 4 is a bottom plan view of the lens shown in FIG. 2, showing the source-remote face of its bottom;

FIG. 5 is a sectional view taken along line 5-5 of FIG. 3, showing half the bottom and also showing in elevation half the source-addressed face of one end of the lens;

FIG. 6 is an end elevation showing the source-remote face on an end of the lens;

FIG. 7 is a side elevation showing half of the source-remote surface of the bottom of the lens;

FIG. 8 is a sectional view taken along line 8-8 of FIGS. 3 and 5, and showing half the source-addressed surface of the bottom in side elevation;

FIG. 9 is a sectional view showing the relationship between the lens shown in FIG. 2 and a mounting fixture thereof;

FIG. 10 is a sectional view on enlarged scale, taken along line 10-10 of FIG. 3;

FIG. 11 is a sectional view on enlarged scale, taken along line 11-11 of FIG. 3;

FIG. 12 is a sectional view on enlarged scale, taken along line 12-12 of FIG. 3;

FIG. 13 is a sectional view on enlarged scale, taken along line 13-13 ofFIG. 3;

FIG. 14 is a sectional view on enlarged scale, taken along line 14-14 of FIG. 3;

FIG. 15 is a perspective view of another fonn of lens suitable for use in the fixture shown in FIG. 9 when the corridor is narrower than that shown in FIG. 1;

FIG. 16 is a top plan view of the lens shown in FIG. 15, as seen from the source-addressed face of its bottom;

FIG. 17 is a bottom plan view of the lens shown in FIG. 15, as seen from the source-remote face of its bottom;

FIG. 18 is a partial sectional view taken along line 18-18 of FIG. 17;

FIG. 19 is an end elevation showing the source-remote face on an end of the lens shown in FIG. 15;

FIG. 20 is a half-side elevation showing part of the sourceremote surface of the bottom of the lens of FIG. 15;

FIG. 21 is a sectional view taken along line 21-21 of FIG. 16;

FIG. 22 is an enlarged sectional view taken along line 22-22 of FIG. 16;

FIG. 23 is an enlarged sectional view taken along lines 23-23 of FIG. 16;

FIGS. 24 and 25 are photometric curves showing the light distribution accomplished by the lens of FIG. 2 when energized by incandescent lamp bulbs of different wattage; and

FIGS. 26 and 27 are photometric curves showing the light distribution accomplished by the lens of FIG. 15 when energized by incandescent lamp bulbs of different wattage.

In FIG. 1, there is diagrammatically shown a typical building corridor of the relatively wide variety exemplified by a lO-foot spacing between opposite sidewalls, and an 8-foot spacing between the floor and ceiling. Such a side corridor is preferably illuminated by fixtures 1, provided with lenses of the character shown in FIGS. 2 through 14, such fixtures being disposed at 8-foot center-to-center spacing lengthwise of the corridor. While, in FIG. 1, only one sidewall of the corridor is shown, it will be understood that a comparable opposite sidewall is intended to be present and spaced from the fixture 1 a distance equal to that at which the sidewall shown is so spaced.

In FIG. 1, the ceiling, the sidewall, and the floor areas shown are subdivided into rows and tiers of squares, each having an area of 4 square feet. The several rows of squares are denominated A through N, and the several tiers are denominated through S. Such delineation of the ceiling, sidewall, and lighting forms no part of the invention, and would seldom, if ever, be sensible in a corridor illuminated in accordance with the invention, but does serve to identify the location of the respective 4 square-foot squares with respect to the illumination values to be stated hereinafter.

The lens 2 is a dish-shaped molded structure of glass or other moldable transparent material. It has a substantially square open top or aperture, and two opposite end walls 3 which are generally triangular in elevation. Closing the space between the end walls 3, there are bottom or side sections 4 which converge downwardly toward a valley to form a generally trough-shaped structure. The inside faces of both end walls 3 are prismatic and the mirror image of each other. The inside faces of the converging sections 4 are prismatic and the mirror image of each other. Likewise, the outside faces of the end walls 3 are prismatic and the mirror image of each other; and the outside faces of the sections 4 are prismatic and the mirror image of each other. In the embodiment shown, the included angle between opposite sections 4 is approximately 140. The end walls 3 are substantially vertical, but, as shown in FIG. 7, sufficiently depart from true vertical, as by about 5, to enable the lens to be separated from a male mold part on which it is formed.

The outside face of the converging sections 4 has, in each half thereof, an array of prisms whose apices run transversely to the valley 5. As clearly seen in FIG. 8, each half (endwardly from line 5-5 in FIG. 3) of the exterior face of the converging sections 4 has its prisms divided into five different subarrays 11, 12, 13, 14 and 15, each of different proportions. The substantially vertical portions 110, 120, 130, 140 and 150, of the respective prisms are hereinafter denominated the risers, and each departs from vertical sufficient to provide the necessary draft for removal of the lens from its mold, but such departure from vertical progressively increases through subarrays 11, 12, 13, 14 and 15, as indicated in the following table:

Subarray Departure Of Riser From Vertical The sloping portions or hypotenuses 111, 121, 131, 141, and 151, which form the opposite face of the respective dihedrals, however, progressively increase in slope from subarray 11 through subarray 15 as indicated in the following table:

Subarray Departure of Hypotenuses From Horizontal The inside face of the converging sections 4 has a prismatic surface of different organization in which the apices of the prisms run parallel to the lengthwise direction of the corridor, i.e., in displacement from the orientation of the prism apices on the outside face of the converging sections 4. As in the case of the prismatic structure on the exterior, however, that on the interior face is divided into halves with the prismatic array on one side of the valley 5 being the mirror image of that on the other side of the valley, as clearly seen in FIG. 3, while the detail of the several prisms is best shown in FIGS. 5 and 10 through 14. From FIG. 5, it will be observed that the array of prisms on the inside face of one of the converging sections 4 is composed of four subarrays 22, 23, 24 and 25. In all such prisms, regardless of the subarray in which it is situated, the dihedral is formed by a face which is substantially vertical (save for draft), hereinafter termed a riser, and another face, hereinafter termed a plateau, which makes a dihedral angle in excess of 90 with the associated riser. In the embodiment shown, the risers in the subarrays 22-25 are uniformly 5 off vertical, but the slope of the plateaus, and hence the dihedral angles, vary as indicated by the following table:

Subarray Departure Ol' Plateau From Horizontal The prismatic structure on the interior face of end walls 3 is apparent from FIGS. 3 and 8, and consists ofa succession of identical prisms 31, whose dihedralsare 90. Typically the valleys of such prisms may be about five sixty-fourths of an inch deep, and their interapice spacing about five thirty-seconds of an inch. As will be observed from FIGS. 3 and 4, the apices of the prisms 31 are tangent with one plane in the left half of the array shown at either end in FIG. 3, and tangent with a different plane in the right half of the respective arrays, so that at the line of valley 5, the prisms at opposite ends are closer to each other than are the prisms more distant (right or left) from the valley 5. The latter arrangement is the result of a transverse concavity in the end walls 3, shown clearly in FIG. 4, and is a control upon sidewise spreading of light transmitted through the end walls while upward-downward spread is controlled by cross-related companion arrays of prisms on the exterior of the end walls, to be described below. As seen in the elevation of FIG. 5, the apices and valleys of the prisms 31 run vertically, but in the 90 related elevation shown in FIG. 8, it will be observed that the apices of the prisms 31 are off vertical about 5, or sufficient to permit the necessary draft for the removal of the male part of a mold in which the lens is cast, as well as to contribute to the control of upward-downward spread of the transmitted light.

As seen in FIGS. 6 and 8, on the exterior of the end walls 3, there are arrays of prisms 32 whose apices run substantially horizontally, and whose dihedral angles are approximately 60, but whose orientation is such that the downwardly and outwardly sloping faces 33 make an angle of approximately 45 with a horizontal plane, while the downwardly and inwardly sloping faces 34 make an angle of approximately with a horizontal plane. This arrangement minimizes the amount of light which emerges from the array of prisms 32 with an upward cast, and, in combination with the prisms 31 on the inside of the end walls, eliminates the occurrence of bright spots within i1 0 of the normal line of sight of a person traversing a corridor lengthwise.

For supporting the lens 3 and accommodating a source of light, any suitable fixture 1 may be employed. Preferably, the entire fixture, save the lens and its supporting framework, is recessed within the ceiling, and a typical example of such a fixture is illustrated in FIG. 9. Such a fixture may comprise a housing 6 enclosing a reflector 7, which is preferably a squarebased, open bottom, truncated pyramid capped by a dome, and having accommodations for a socket 8 within which is received a globular light source, such as an incandescent lamp bulb, or a mercury vapor lamp bulb, in a position such that the entire bulb is preferably disposed above the aperture of the reflector, and hence entirely above the lens 2. It will be understood that when the installation is being made in a relatively narrow corridor, such as one 8 feet wide, the lens 2 is preferably replaced in the fixture 1 by a lens such as that shown in FIGS. 15 through 21, now to be described.

To be interchangeable with the lens 2, the lens 40, shown in FIG. 15, has the same dimensions at its open top or aperture as does the lens 2, and the same arrangements for mounting the lens in the fixture shown in FIG. 9 may be provided. Since the lens 40 is intended to be used in narrower corridors than the lens 2, the lens 40 is provided with light refracting and reflecting means for restricting the spread of lens-transmitted light in the direction crosswise of the corridor to a degree less than that accomplished by the lens 2. However, since each lens, when energized by the same type and wattage of globular light source, will deliver the same total amount of light, it is desirable to construct the light reflecting and refracting means in the lens 40 so that the cross-corridor reduction in distribution of light is compensated for by along-corridor increase of the light distribution, and consequently it is possible, with such a lens, to increase the center-to-center spacing between fixtures in the same proportion as the corridor width is diminished.

As in the case of the previous embodiment, the lens 40 is a dish-shaped structure having opposite end walls 43. Interconnecting the end walls, there is a series of reentrantly converging sections 41, 42, 44 and 45, which have prismatic surfaces on both the interior and exterior faces thereof. Such converg ing sections together constitute the bottom and sides of a trough-shaped lens having a W-shaped cross-sectional configuration.

The W-shaped contour of the end walls 43 provides each end of the lens 40 with approximately one-third more end wall area than that of the lens 2 at the same width and depth, and consequently a greater amount of light can be transmitted through the end walls of lens 40 than through the end walls of lens 2, thereby increasing the along-corridor light spread over that achieved by the lens 2. On the other hand, the reentrant configuration of the bottom sections 41, 42, 44 and 45 and their relative angular disposition, together with the configuration of the prismatic surfaces thereof, reduce both the sidewise spread and the overall amount of light transmitted therethrough as to conform with the reduced cross-corridor requirements of the narrower corridor in which the lens is installed.

As in the case of the lens 2, the ends 43 of the lens 40 have, on their interiors, a prismatic surface in which prisms 46, with dihedrals, have their apices extending substantially vertically in the manner described in connection with the prisms 31 of the previous embodiment. The detail of this array of prisms is identical with that described in connection with the previous embodiment. On the exterior faces of the end walls 43, there is an array of prisms 47 whose apices extend substantially horizontally, and whose dihedrals and orientation may be exactly as described in connection with the prisms 32 of the previous embodiment.

The exterior face of the reentrantly converging sections 41, 42, 44 and 45 is shown in plan in FIG. 17, and consists of an array of prisms whose apices are parallel with the end walls 43, and which, save for a central belt amounting to somewhat less than a third the length of the lens, have substantially vertical (with draft) risers and hypotenuses comparable with the subarrays 12, 13, and 14 of the previous embodiment, and are designated 112, 113, and 114 in FIG. 21, which differ from each other in dihedral angle as follows:

Sub-array Dihedral Angle On the other hand, the prisms in the central belt 115 have no substantially vertical risers, but instead are isosceles in cross section with bases twice as wide as the other subarrays, and whose dihedrals are except for the center one where the dihedral is The inside face of the reentrant sections 41 and 45 have prismatic surfaces which are the mirror image of each other, and so do the reentrant sections 42 and 44. FIG. 18 shows generally the inside prismatic structure of sections 44 and 45, and the detail thereof is shown in FIGS. 22 and 23, respectively.

As seen in FIGS. 18 and 22, the array of prisms on the inside of section 44 have their apices substantially tangent with a plane which tilts downwardly and outwardly from the center line (longitudinally of the corridor) of the lens at an angle of about 856 with the horizontal; and the risers 440 depart from vertical in the same degree while forming an acute dihedral with an adjacent hypotenuse 441. The interapicial spacing may be a constant, such as five thirty-second inch, and the acuity of such dihedral increases from the center line outwardly in three subarrays 442, 443, and 444, as follows:

At the center line, however, there is no riser as two oppositely oriented hypotenuses intersect to form a dihedral of 153.

On the inner face of sections 41 and 45, there is a prism array in which the individual prisms have obtuse dihedrals, and are spaced so as to reflect, in the endwise direction, about as much incident light as they refract in the sidewise direction. The detail of these prisms is shown in FIG. 23, and each has a riser 450 which intersects with a plateau 451 to form an obtuse dihedral, but each plateau is separated from the next succeeding riser by an intervening flat 452, all oriented so that the plane of the flats slopes upwardly and outwardly at an angle of about 35 with the horizontal. This array of prisms and flats is divided into three subarrays 453, 454 and 455, in which the interapicial spacing is a constant five thirty-second inch; in which the plane of each riser intersects (as shown in dotted lines in FIG. 23) the plane of the plateau next below it at a constant one thirty-second inch below the plane of the flats 452; and in which the angles are as follows:

In the several perspectives (FIGS. 2 and end elevations (FIGS. 6 and 19), side elevations (FIGS. 7 and and bottom plan views (FIGS. 4 and 17), it will be observed that the corners between the end walls and the bottom sections are stippled. Such stippling is to indicate that the corners are not only beveled, but provided with a series of miniscule notches sufficiently close together to diffuse any light emerging from such corners of the lens.

The patterns of light distribution achieved by the fixture shown in FIG 9, when equipped with the lenses of the invention, are illustrated in FIGS. 24 through 27, in each of which the broken line photometric curve represents the distribution in the direction which would correspond with the lengthwise dimension of a corridor, and the solid line photometric curve represents the distribution in the direction which corresponds with the cross dimension of a corridor. FIG. 24 represents the performance of the lens shown in FIG. 2 when energized with a 200 watt incandescent lamp, while FIG. represents the performance of the same lens but utilizing a 300 watt incandescent lamp. FIGS. 26 and 27, on the other hand, represent the performance of the same fixture when equipped with the lens of FIG. 15, and energized, respectively, with a 200 watt and with a 300 watt incandescent lamp. Comparison between the broken line curves in FIGS. 24 and 26 reveals the greater spread of light lengthwise of a corridor when the lens of FIG. 15 is employed, and comparison of the solid line curves reveals the greater spread of light widthwise and into the corners between the floor and the sidewalls when the lens of FIG. 2 is employed. The same comparisons apply to FIG. 25 versus FIG. 27, which differ from FIGS. 24 and 26 only to an extent attributable to the wattage of the bulbs employed. Noteworthy is the fact neither lens emits measurable light in the direction above 90, which would be toward the ceiling of a corridor, it being a feature of the invention that corridor ceiling illumination is achieved substantially by light reflected from other corridor surfaces. Noteworthy also is the fact that none of the along-the-corridor curves has a slope such as to be tangent with the 60 radius.

A more practical, and persuasive, set of data is tabulated below and shows the performance of the lenses of the present invention in actual use in corridors of different dimensions, but wherein the ceilings had a reflectance factor of 80 percent, the sidewalls a reflectance factor of 50 percent, and the floors a reflectance factor of percent. Under these conditions, the respective lenses were tested with various lamps at different fixture spacings in corridors of differing widths, and the illumination measured with a light meter in each of the 4 square-foot squares delineated in FIG. 1, wherein, as previously explained, the letters A through N represent the different rows (running lengthwise of the corridor, whether in the ceiling, sidewall, or floor), and the letters 0 through S represent different tiers (running crosswise of the rows). Thus, a square designated as J-O means the square in row J and tier 0, i.e., the square in the floor at the left comer nearest the reader of FIG. 1. The recorded results as tabulated below, therefore, represent not only the light which emanates from the lens and directly impinges upon a given square, but rather the total light impinging upon the given square at a given instant, regardless of whether that light was direct from the lens or reflected to that square from another increment of the corridor enclosing surfaces. The results obtained with the lens of FIG. 2 in a corridor 10 feet wide, having an 8-foot ceiling, from fixtures spaced on 8-foot centers centrally of the ceiling, and with various lamps, are tabulated below:

FOOT-CANDLES ON FIG. 1 SQUARES FIG. 2 Lens-8 Foot Spacing In Corridor 10 Feet Wide, 8 Foot Ceiling with various lamps Square Incandescent Mercury 200w. 300w. w. w.

A-O Ceiling l2 l9 10 2| A4 ll 17 9 20 A-Q ll 17 9 20 A-R l2 l9 I0 21 B-0 [3 20 I0 21 B-P l2 l9 9 20 13-0 l2 l9 9 20 B-R I3 20 10 21 C-0 14 22 i2 22 C-P I3 20 IO 20 C-0 [3 20 It) 20 C-R I4 22 I2 22 D-O 13 20 I0 21 D-P l2 l9 9 20 D-O l2 l9 9 20 D-R 13 20 10 2I E-O l2 I9 10 21 E-P l 1 l7 9 20 E-O ll l7 9 20 E-R Ceiling l2 l9 I0 21 F-O Wall 18 28 I4 29 F4 15 23 ll 26 F-Q i5 23 ll 26 F-R I8 28 I4 29 G-O I9 3O 16 32 6-? I6 25 I3 28 G-Q 16 25 I3 28 G-R I9 30 16 32 H-0 20 32 18 34 H-P I7 27 IS 30 H-Q I7 27 15 30 H-R 20 32 I8 34 l-O 20 32 17 34 I-P 19 30 I5 32 [-0 I9 30 I5 32 I-R Wall 20 17 34 J-O Floor 27 43 23 42 .l-P 25 40 2] 40 J-Q 25 40 ll 40 141 27 43 23 42 K-0 30 48 26 S0 K-P 28 45 25 48 K() 28 45 25 48 K-R 30 48 26 50 L-P 30 48 27 52 L-Q 30 48 27 52 L-R 32 50 28 53 M-O 3O 48 26 50 M-P Z8 45 25 4?! The results obtained with the lens of FIG. 15 in a corridor feet wide, having an 8-foot ceiling, with fixtures spaced on 10- foot centers centrally of the ceiling, and with various lamps, are tabulated below:

FOOT-CANDLES ON FIG. 1 SQUARES Fig. 15 Lens-l Foot Spacing ln Corridor 8 Feet Wide, 8

Foot Ceiling with various lamps Square Incandescent Mercury 200w. 300w. 100w. 175w.

B-O Ceiling 1 l l7 9 19 B-P l0 l6 9 19 8-0 9 l5 8 17 B-R l0 l6 9 19 8-8 1 1 l7 9 19 C-0 13 20 22 C-P l l 17 9 19 C-0 l0 l6 8 1B C-R l l 17 9 19 C-S 13 10 22 D-O 13 20 10 22 DP l 1 l7 9 19 D-Q l0 l6 8 18 D-R l 1 l7 9 19 D-S 13 20 10 22 E0 l l 17 9 19 5-? l0 l6 9 19 E-Q 9 l5 8 17 E-R l0 l6 9 19 5-8 Ceiling l1 l7 9 19 FO W all 23 37 20 39 F-P 21 33 18 36 F-Q I6 25 13 26 F-R 21 33 18 36 F-S 23 37 20 39 6-0 24 38 20 40 (3-? 23 36 19 37 6-0 17 26 13 29 G-R 23 36 19 37 (3-5 24 38 20 40 H-0 22 34 19 38 H-P 21 33 18 35 1-1-0 16 25 14 29 l-l-R 21 33 18 35 l-l-S 22 34 19 38 l0 19 3O 17 34 l-P I9 30 17 33 1-0 l5 24 14 28 l-R I9 30 17 33 l-S Wall 19 30 17 34 1-0 Floor 23 36 21 42 1-1 23 37 22 41 1-0 22 3 5 19 37 J-R 23 37 22 41 1-5 23 36 21 42 K-0 27 42 24 49 K4 27 43 25 48 K-0 28 44 23 44 K-R 27 43 25 48 K-S 27 42 24 49 L-O 27 42 24 49 L-P 27 43 25 48 L-Q 28 44 23 44 L-R 27 43 25 48 LS 27 42 24 49 M-O 23 36 21 42 MP 23 37 22 41 M-Q 22 19 37 M-R 23 37 22 41 M-S Floor 23 36 21 42 From the foregoing description, those skilled in the art should readily understand that the invention accomplishes its objects. While two embodiments of the lens of the invention have been described in detail, and the differences in their results recited, it is not to be understood that the invention is limited to the details of such embodiments.

Having thus described the invention, what I claimed and desired to be secured by Letters Patent is:

1. A luminaire for a corridor having length, height and width comprising a light source centered on an axis Y parallel with the height of said corridor, a lens mounted below said light source substantially coaxially with axis Y, said lens being dish-shaped and having:

a. an axis X parallel with the length of said corridor;

b. an axis Z parallel with the width of said corridor;

c. opposite end walls having a major dimension parallel with the Z axis and a minor dimension parallel with the Y axis;

d. a bottom reversely sloping in the direction of Y relative to Z; each of said end walls having:

e. an array of prisms whose lateral edges extends substantially parallel with the Y axis and with each other on its interior surface; and

f. an array of prisms whose lateral edges extend substantially parallel with the Z axis and with each other on the exterior surface thereof; and said bottom having:

g. an array of prisms whose lateral edges extend substantially parallel with the X axis on its interior surface, and each prism including a substantially vertically disposed riser arranged parallel with a plane including the X and Y axes, and a plateau that is disposed more horizontally than to the vertical, said plateau being more nearly parallel with a plane including the X and Z axis than with said X-Y plane; and

h. an array of prisms whose respective lateral edges lie in planes substantially parallel with the Y and Z axes on its exterior surface.

2. The luminaire of claim 1 wherein the end walls of the lens have a V-shaped marginal configuration in the plane which includes the Y and Z axes, and the maximum Y axis dimension of said end walls is substantially in a plane including the X and Y axes.

3. The luminaire of claim 1 wherein the end walls of the lens have a W-shaped marginal configuration, and their maximum Y axis dimension is at a position substantially spaced in the direction of the Z axis from a plane including the X and Y axes.

4. A trough-shaped lens having a substantially rectangular open top, substantially parallel walls at opposite ends of said open top and projecting substantially vertically downward therefrom, and sloping sections extending downwardly and inwardly at opposite sides of said open top and interconnecting said walls, each of said walls having:

a. on its interior surface an array of substantially equispaced and equisized prisms having rectilinear apices which extend substantially vertically, and

b. on its exterior surface an array of substantially equispaced and equisized prisms having rectilinear apices which extends substantially horizontally, said sloping sections having:

c. on their interior surface an array of prisms whose apices are substantially perpendicular to said walls, said apices being formed by a substantially vertical riser and an intersecting dihedral forming surface having substantially greater area than said riser, said dihedral forming surface being disposed more horizontally than to the vertical, and

. on the exterior surface an array of prisms having apices lying respectively in parallel planes which are substantially parallel with said wall, said apices being formed by a substantially vertical riser and an intersecting dihedral forming surface having substantially greater area than said riser.

5. The lens of claim 4 in which said sloping sections converge to form a V-shaped valley; and the arrays of prisms (c) and (d) on opposite slopes of the valley are respectively the mirror image of each other.

6 The lens of claim wherein the dihedral forming surfaces disposed upon the interior surface of the sloping sections are greater in area where said sloping sections converge to form the juncture of the V-shaped valley than the area of the dihedral fonning surfaces located remotely from said juncture.

"I. The lens of claim 5 wherein the risers fonning the exterior surface of the sloping sections are of greater depth at their location proximate the end walls than at the center of said lens between said end walls.

8. The lens of claim 4 in which said sloping sections have reentrant portions which converge to form a W-shaped valley; the arrays of prisms (c) and (d) on said portions which join each other in an inverter V being the mirror image of each other; and the arrays of prisms (c) and (d) on said portions which are outwardly of said inverted V being the mirror image of each other.

9. The invention of claim 8 wherein the vertical risers formed on the exterior surface of said sloping sections are of greater depth at their location proximate the end walls than the depth of the risers located closer to the center of said lens between said end walls. 

1. A luminaire for a corridor having length, height and width comprising a light source centered on an axis Y parallel with the height of said corridor, a lens mounted below said light source substantially coaxially with axis Y, said lens being dish-shaped and having: a. an axis X parallel with the length of said corridor; b. an axis Z parallel with the width of said corridor; c. opposite end walls having a major dimension parallel with the Z axis and a minor dimension parallel with the Y axis; d. a bottom reversely sloping in the direction of Y relative to Z; each of said end walls having: e. an array of prisms whose lateral edges extends substantially parallel with the Y axis and with each other on its interior surface; and f. an array of prisms whose lateral edges extend substantially parallel with the Z axis and with each other on the exterior surface thereof; and said bottom having: g. an array of prisms whose lateral edges extend substantially parallel with the X axis on its interior surface, and each prism including a substantially vertically disposed riser arranged parallel with a plane including the X and Y axes, and a plateau that is disposed more horizontally than to the vertical, said plateau being more nearly parallel with a plane including the X and Z axis than with said X-Y plane; and h. an array of prisms whose respective lateral edges lie in planes substantially parallel with the Y and Z axes on its exterior surface.
 2. The luminaire of claim 1 wherein the end walls of the lens have a V-shaped marginal configuration in the plane which includes the Y and Z axes, and the maximum Y axis dimension of said end walls is substantially in a plane including the X and Y axes.
 3. The luminaire of claim 1 wherein the end walls of the lens have a W-shaped marginal configuration, and their maximum Y axis dimension is at a position substantially spaced in the direction of the Z axis from a plane including the X and Y axes.
 4. A trough-shaped lens having a substantially rectangular open top, substantially parallel walls at opposite ends of said open top and projecting substantially vertically downward therefrom, and sloping sections extending downwardly and inwardly at opposite sides of said open top and interconnecting said walls, each of said walls having: a. on its interior surface an array of substantially equispaced and equisized prisms having rectilinear apices which extend substantially vertically, and b. on its exterior surface an array of substantially equispaced and equisized prisms having rectilinear apices which extends substantially horizontally, said sloping sections having: c. on their interior surface an array of prisms whose apices are substantially perpendicular to said walls, said apices being formed by a substantially vertical riser and an intersecting dihedral forming surface having substantially greater area than said riser, said dihedral forming surface being disposed more horizontally than to the vertical, and d. on the exterior surface an array of prisms having apices lying respectively in parallel planes which are substantially parallel with said wall, said apices being formed by a substantially vertical riser and an intersecting dihedral forming surface having substantially greater area than said riser.
 5. The lens of claim 4 in which said sloping sections converge to form a V-shaped valley; and the arrays of prisms (c) and (d) on opposite slopes of the valley are respectively the mirror image of each other.
 6. The lens of claim 5 wherein the dihedral forming surfaces disposed upon the interior surface of the sloping sections are greater in area where said sloping sections converge to form the juncture of the V-shaped valley than the area of the dihedral forming surfaces located remotely from said juncture.
 7. The lens of claim 5 wherein the risers forming the exterior surface of the sloping sections are of greater depth at their location proximate the end walls than at the center of said lens between said end walls.
 8. The lens of claim 4 in which said sloping sections have reentrant portions which converge to form a W-shaped valley; the arrays of prisms (c) and (d) on said portions which join each other in an inverter V being the mirror image of each other; and the arrays of prisms (c) and (d) on said portions which are outwardly of said inverted V being the mirror image of each other.
 9. The invention of claim 8 wherein the vertical risers formed on the exterior surface of said sloping sections are of greater depth at their location proximate the end walls than the depth of the risers located closer to the center of said lens between said end walls. 